The difficulty level cannot be known for sure since there has been only one question paper(2017) on the revised syllabus so far. But as for the preparation, you can refer the NCERT - Exemplar Mathematics(11 + 12) books. Also the NATA - Mock Tests on edge incorporate the same difficulty as the last year paper.
Access the All India Mock Test Series. Each test has 2 sections, Section 1 is your Aptitude + Math and Section 2: Drawing is the drawing section. Each test has 2 drawing questions which means a total of 2 * 10 = 20 questions for practice.
you can know the architects and there works in reference books like arihant etc books
try youtub so many options on this qus.